Numerical and experimental investigations of self-piercing riveting

Self-pierce riveting (SPR) is a new high-speed mechanical fastening technique which is suitable for point joining dissimilar sheet materials, as well as coated and pre-painted sheet materials. With increasing application of SPR in different industrial fields, the demand for a better understanding of the knowledge of static and dynamic characteristics of the SPR joints is required. In this paper, the SPR process has been numerically simulated using the commercial finite element (FE) software LS-Dyna. For validating the numerical simulation of the SPR process, experimental tests on specimens made of aluminium alloy have been carried out. The online window monitoring technique was introdu introdu ced in the tests for evaluating the quality of SPR joints. Good agreements between the simulations and the tests have been found, both with respect to the force-travel (time) curves as well as the deformed shape on the cross-section of SPR joint. Monotonic tensile tests were carried out to measure the ultimate tensile strengths for SPR joints with different material combinations. Deformation and failure of the SPR joints under monotonic tensile loading were studied. The normal hypothesis tests were performed to examine the rationality of the test data. This work was also aimed at evaluating experimentally and comparing the strength and energy absorption of SPR joints and SPR-bonded hybrid joints

Study on forced vibration behavior of adhesively bonded single-lap joint

With the increase in the use of adhesively bonding in primary structures, reliable and cost-effective techniques for structural health monitoring of adhesive bonding are needed. Vibration-based tests, when combined with validated FEA, can provide a key tool for structural health monitoring of adhesive bonding. This paper deals with forced vibration behavior of adhesively bonded single-lap joint theoretically and experimentally. The finite element analysis (FEA) software was used to predict the natural frequencies, mode shapes and frequency response functions (FRFs) of the joint. The dynamic test software and the data acquisition hardware were used in experimental measurement of the dynamic response of the joint. The predicted results were compared with experimentally measured ones to validate the prediction technique. It was found that the forced vibration behavior predicted from FEA matches reasonably well with the experimental observations. It can be concluded that the FEA of the forced vibration behavior of adhesively bonded single-lap joint will help future applications of adhesive bonding by allowing different parameters to be selected to give as large a process window as possible for adhesively bonded joints vibration analysis

Numerical study on free vibration characteristics of encastre clinched joints

The present paper deals with free vibration analysis of single lap encastre clinched joints using three dimensional finite element methods. The focus of the analysis is to reveal the influence on the natural frequencies, natural frequency ratios and mode shapes of these joints caused by variations in the material properties of the sheet materials. Numerical examples show that natural frequencies of single lap encastre clinched joints increase significantly as the Young’s modulus of the sheets increase, but only slight changes are encountered for variations of Poisson’s ratios. The mode shapes show that there are different deformations in the jointed section of clinched joints. These different deformations may cause different natural frequency values and different stress distributions. In both cases of transverse free vibration and torsional free vibration, odd mode shapes were found to be symmetrical about the mid-length position and even mode shaps were anti-symmetrical. The amplitudes of vibration at the mid-length of the joints are different for the odd and even modes. The geometry of the lap section is therefore very important and has a very significant effect on the dynamic response of the single lap encastre clinched joints. The main goal of this paper is to give an outline of free vibration characteristics of encastre clinched joints by finite element methods and to provide a basis for further experimental research

An Analytical Model for Predicting the Stress Distributions within Single-Lap Adhesively Bonded Beams

An analytical model for predicting the stress distributions within single-lap adhesively bonded beams under tension is presented in this paper. By combining the governing equations of each adherend with the joint kinematics, the overall system of governing equations can be obtained. Both the adherends and the adhesive are assumed to be under plane strain condition. With suitable boundary conditions, the stress distribution of the adhesive in the longitudinal direction is determined

Risk of venous thromboembolism with janus kinase inhibitors in inflammatory immune diseases: a systematic review and meta-analysis

Objectives: This study aimed to evaluate the risk of venous thrombosis (VTE) associated with Janus kinase (JAK) inhibitors in patients diagnosed with immune-mediated inflammatory diseases.Methods: We conducted a comprehensive search of PUBMED, Cochrane, and Embase databases for randomized controlled trials evaluating venous thromboembolic incidence after administering JAK inhibitors in patients with immune-mediated inflammatory diseases. The studies were screened according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and a meta-analysis was performed.Results: A total of 16 studies, enrolling 17,242 participants, were included in this review. Four approved doses of JAK inhibitors were administered in the included studies. The meta-analysis revealed no significant difference in the incidence of VTE between patients receiving JAK inhibitors, a placebo, or tumor necrosis factor (TNF) inhibitors (RR 0.72, 95% CI (0.33-1.55); RR 0.94, 95%CI (0.33-2.69)). Subgroup analysis showed a lower risk of VTE with lower doses of JAK inhibitors [RR 0.56, 95%CI (0.36-0.88)]. Compared with the higher dose of tofacitinib, the lower dose was associated with a lower risk of pulmonary embolism [RR 0.37, 95%CI (0.18-0.78)].Conclusion: Our meta-analysis of randomized controlled trials observed a potential increase in the risk of VTE in patients with immune-mediated inflammatory diseases treated with JAK inhibitors compared to placebo or tumor necrosis factor inhibitors, though statistical significance was not attained. Notably, a higher risk of pulmonary embolism was observed with high doses of tofacitinib. Our findings provide valuable insights for physicians when evaluating the use of JAK inhibitors for patients with immune-mediated inflammatory diseases.Systematic Review Registration:https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023382544, identifier CRD4202338254